I meant to state EEPROM.

Let's forget about the features, like the RAM.

Let's start with a bare bones 8051 system, using an 80C51BH from Intel, a 12Mhz crystal, one LED light, one resistor, and the 32KB (256 kilobit) EEPROM.

I can design this as a "system", but I want to add the parallel port to the data lines (which I should be able to do), and be able to program the EEPROM using only the component setup I mentioned above.

I can see that forcing the "NOP" command on the microprocessor will cause the internal microprocessor address to increment by one. This will eliminate my need for counters.

The reason why I want to control whether the microprocessor has a running crystal or not, is because I want to use the same board, in the same circuit configuration, both for programming the EEPROM from the parallel port, and for running the code from the EEPROM. If I don't use proper timing in programming the EEPROM, then it won't be programmed. Programming an EEPROM is slower than reading from it.

Once I get the basic setup down pat, then I can worry about the features, like RAM, etc.



to sum this all up, I want to make an 8051 based PC whose EEPROM code can be changed by today's computers that use a parallel port.

I am experienced with the use of the parallel port, so I don't need help with its usage.